Fix a bug in nesting check_sparse_tensor_invariants context managers (#95372)
As in the title. The bug was reported in https://github.com/pytorch/pytorch/pull/94728#discussion_r1108892366 and has the following reproducer:
```python
>>> import torch
>>> check_ctx = torch.sparse.check_sparse_tensor_invariants(True)
>>> no_check_ctx = torch.sparse.check_sparse_tensor_invariants(False)
>>> with check_ctx:
... assert torch.sparse.check_sparse_tensor_invariants.is_enabled()
... with no_check_ctx:
... assert not torch.sparse.check_sparse_tensor_invariants.is_enabled()
... assert torch.sparse.check_sparse_tensor_invariants.is_enabled()
...
Traceback (most recent call last):
File "<stdin>", line 5, in <module>
AssertionError
```
Pull Request resolved: https://github.com/pytorch/pytorch/pull/95372
Approved by: https://github.com/cpuhrsch
